An on-vehicle radar and a projection-type optical scanner scanning a light beam emitted from a light source, such as a laser or an LED, in two-axis directions perpendicular to each other have been commercialized. Each of these optical scanners includes a light source, an actuator, and an actuator drive device that drives and controls the actuator.
The actuator includes a reflector, a driver for rotating the reflector, and a drive electrode for vibrating the driver. The driver rotates the reflector about two operational axes perpendicular to each other. The drive electrode vibrates and drives the driver such that the reflector can rotate and vibrate at a predetermined drive frequency. The reflector reflects a light beam emitted from the light source, and, for instance, scans the light beam in two-dimensional directions as to display an image by raster scanning. In this case, the actuator drives the reflector in a horizontal direction with a sine wave, and drives the reflector in the vertical direction with a saw-tooth wave.
Patent Literature 1 discloses a conventional actuator.
This actuator drives a reflector with a saw-tooth wave, thereby displaying an image. If a drive signal contains a resonance frequency peculiar to the actuator, the reflector may vibrate with an unintended waveform. Patent Literature 1 also discloses that a component of the resonance frequency contributing to the unintended vibration is removed from the driving signal so as to suppress the resonant vibration.
The removal of the component of the resonance frequency from the drive signal, however, degrades a linearity of the drive signal, and for instance, may produce a distortion of the image displayed by the optical scanner, thus causing the image quality to deteriorate.